Hitherto, in a surgery such as cataract, a treatment is performed in which an incision is provided in an eye tissue such as a cornea (sclera) or an anterior lens capsule in an eyeball, a lens in a capsule is extracted and removed through the incision, and then an intraocular lens as a replacement for the lens is inserted from the incision into an eye so as to be disposed inside the capsule.
Particularly, in recent years, an insertion apparatus to be described below is used in many cases when inserting the intraocular lens from the incision into the eyeball. That is, the intraocular lens is inserted into the eyeball in a manner such that a leading end opening of an insertion tube provided in a leading end of the apparatus body is inserted into an eyeball through an incision and the intraocular lens is extruded by a rod-like plunger from the leading end opening of the insertion tube while being compactly deformed inside the apparatus body (for example, see Patent Literatures 1 to 3). Since such an insertion apparatus is used, the intraocular lens may be simply inserted into the eyeball using the incision provided to extract and remove the lens. For this reason, the surgery may be simplified and hence an occurrence of astigma or infection after the surgery may be suppressed.
Incidentally, in the operation of inserting the intraocular lens, there is a demand to further decrease the sizes of the incision and the leading end of the insertion tube in the insertion apparatus in order to reduce the patient's burden during the surgery. However, when the leading end of the insertion tube decreases in size, the diameter of the plunger needs to be decreased. Meanwhile, when the insertion tube decreases in size, the intraocular lens is compressed during the passage through the insertion tube, and hence there is a tendency that the resistance acting on the plunger during the extrusion becomes stronger. As a result, there is a case in which the plunger is deformed when extruding the intraocular lens from the insertion apparatus, so that the operation of inserting the intraocular lens is not stably performed.